1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to synchronization between a multimedia server and a client and, more particularly, to synchronizing multimedia content with a device which supports a multi-server environment.
2. Description of the Related Art
If a user desires to download content such as multimedia files from a server and store the downloaded content in a portable device, it is necessary to perform synchronization with the server. Particularly, as the importance of digital rights management (DRM) increases, studies for maintaining synchronization between content stored in a server and content stored in a portable device have been made. According to a related art content synchronization method, a portable device subject to synchronization, which serves as a client, is connected to the server in a one-to-one manner through an interface such as a Universal Serial Bus (USB), IEEE 1394, and others.
FIG. 1 is a view illustrating a connection between a single content synchronization server and a portable device according to a related art.
Referring to FIG. 1, the related art content synchronization server 10 and the portable device 20 are connected to each other by a wired or wireless connection and then start to synchronize with each other. The content synchronization server 10 senses the connection to the portable device 20 serving as a client to be synchronized with the server, through an interface 30 such as a USB interface or a IEEE 1394 interface. The content synchronization server 10 identifies whether the sensed portable device 20 is a synchronization target device based on additional information of the corresponding portable device 20. If it is identified that the portable device 20 is a synchronization target device, the content synchronization server 10 acquires a synchronization list of a corresponding device through a synchronization list management unit 13.
A synchronization target content collector 15 secures all data relating to synchronization by collecting a content set as a synchronization list among content stored in the content synchronization server and collecting all the content existing in a local storage of the portable device. To perform the synchronization, a synchronization processor 16 compares the content corresponding to the synchronization list of the content synchronization server 10 with all the content existing in the portable device 20, and repeatedly downloads or uploads specified content to the portable device 20 or the content synchronization server 10.
If a collision occurs in the specified content, it is processed by a given policy. In general, the existing content synchronization server adopts a policy of first reflecting content data, which exists in the content synchronization server, in the portable device. If all the content is completely processed, the synchronization ends. When the synchronization is completed, the portable device 20 is filled with the same content as the synchronization list of a corresponding portable device 20 set in the content synchronization server 10.
The related art content synchronization server 10 of FIG. 1 has several problems in synchronization.
First, the content synchronization server 10 is not suitable for a multi-server environment. According to the synchronization method of the content synchronization server 10, one or more portable devices 20 are connected to one content synchronization server 10. In other words, a specified portable device 20 which takes part in automatic synchronization with a specified content synchronization server 10 cannot simultaneously take part in automatic synchronization with another content synchronization server.
Second, the content synchronization server 10 supports only a server based unidirectional policy during the automatic synchronization. This cannot meet various demands of a user under the multi-server environment.
Third, the content synchronization server 10 performs the synchronization by comparing its content with the content of a client regardless of the change of the content. In this case, if a lot of target content exists, it is inefficient in that the synchronization becomes slow regardless of the change of the content.
Specifically, most of changes of files generated in the portable device mean the change in meta data of the content such as the frequency of playbacks and the last playback time. However, the content synchronization server 10 is inefficient in that it performs the content file based synchronization to exchange the whole files when the files are changed due to the change of their meta data, and this causes an inefficient synchronization.
In this respect, the synchronization is performed through multiple content servers, and thus it is required to provide a method and apparatus for synchronizing multimedia content with a device to match the attributes of the multimedia content.